Dr. Fornace isolated a partial cDNA sequence from UV treated Chinese Hamster Ovary cells which displays a unique pattern of expression during cell growth. This clone which was originally isolated because it was induced about 3 fold after treatment with UV is highly expressed in a variety of cell types when growth is inhibited. Using the partial cDNA sequence as a probe we nave recently succeeded in isolating a full length clone corresponding to this gene product and sequenced it in its entirety. Our current studies are aimed at understanding the regulation of this gene and its relationship to cellular senescence as a model for in vitro aging.